Thanks for the help! I did read all those links, but I didn’t see the specific information I’m looking for — how to enable the build box to connect back to the hosted repo via SSH+git.

I’ve managed to get it working but sadly I don’t exactly understand how.

from Q179 :

Second Part : Drydock

Create a blueprint
Home → Drydock → Blueprint → New blueprint
Select almanac host.
Give it a name (like builder-worker-contract), select the almanac service (highly-secure-builder) and create a credential (with private key (from device step) and the user you want that drydock connect to root or something else if you are conscientious).
You can lock the key content if you want too.

Last Part : adding the key and testing

Go on your build host and add the key to {the home directory of the user you chose}/.ssh/authorised_keys2`

If you did like above, and that make it works, i will edit my answer to sum thjat up !